98 



THE NEW KNOWLEDGE. 



They even strike backward upon the radium substance it- 

 self, so that it, too, becomes luminous, and shines vividly 

 with a light which, since the discovery of radium, has shown 

 no shadow of variableness. Becquerel rays by means of this 

 self -phosphorescence will photograph the radium which emits 

 them. Fig. 28 (a) is a picture of some radium chloride 

 photographed by daylight, and Fig. 28 (b) shows the same 

 radium chloride photographed in the dark by its own light 

 a life-size portrait of the first radium chloride in the world 

 executed by itself. They seem strange things, then, these 



Fig. 28 (a). 

 Radium chlo- 

 ride photo- 

 graphed by 

 daylight, by 

 M. Curie. 



Fig. 28 (6). 

 Radium chlo- 

 ride photo- 

 graphed in 

 dark by the 

 light of its 

 own phos- 

 phorescence. 



[To obtain the wonderful photographs shown in Fig. 28 (a and 6), 

 less than T f ^ of a gram of chemically pure radium chloride was utilized 

 by M. Curie. The value of a gram of radium would be $10,000 or more. 

 Less than a gram exists ] 



Becquerel rays from radium and yet strange 'as they are, 

 in this power of causing phosphorescence in bodies which 

 they strike, they exactly resemble the corpuscles of cathode 

 rays, page 69, Part III. 



